What is the defining feature of a rim fire primer?

The defining feature of a rim fire primer is that it detonates when force is applied to any part of the base. This means that the entire rim of the cartridge case is designed to be sensitive, allowing the primer to ignite upon striking a surface, rather than relying on a central striker as in centerfire cartridges. The unique design of the rimfire cartridge, where the primer compound is located in the rim of the cartridge case itself, allows it to work effectively even when struck at different angles or locations along the base.

This concept is crucial for understanding the mechanics of firearms and ammunition types. Rimfire cartridges are generally less powerful than centerfire rounds, and this distinct feature affects how they are loaded and fired. In contrast, other options describe characteristics that don't align with how rimfire primers are designed and operate.